Traditional U.S. retailers are struggling. Office supply store Staples(SPLS) slumped over 12% on lousy earnings and a warning that results in the current period are likely to fall short of expectations. That news also weighed on rival Office Depot(ODP), which fell 6%.

Dick's Sporting Goods(DKS) tumbled 18% after revealing subpar golf and hunting sales that sparked weaker than expected results. Dick's also spooked investors by dimming its sales and earnings outlook for the entire year. The company needs a new round -- or arsenal -- of ideas.

2. Not so pretty looks at Target, Penney and Urban Outfitters

It wasn't much prettier for regular clothing, either. Shares of Urban Outfitters(URBN) fell 9% after the retailer revealed a profit drop that was driven by higher expenses. T.J. Maxx and Marshalls parent TJX(TJX) slid nearly 8% on an earnings and sales miss.

Another struggling retailer, Target(TGT), announced the departure of Canadian chief Tony Fisher, who will be replaced by Mark Schindele. The move comes just weeks after Target dismissed CEO Gregg Steinhafel and amid concerns about continued losses in the company's Canadian division. Target is set to report results Wednesday morning

One of the lone positive retail stories today is Home Depot(HD), which rallied 2% after upgrading its outlook. The rosier view offset concerns over the home improvement retailer's weak first-quarter profits and sales.

Maybe people really are doing their spring cleaning and summer repairs.

Americans might not be shopping much in brick-and-mortar stores, but they're definitely gobbling up Red Robin(RRGB) burgers. The fast food joint's shares popped 13% on a first-quarter earnings beat fueled by sales and margin growth.

4. Remember momentum stocks?

Growth concerns were triggered by Caterpillar(CAT), which said machine sales slumped 13% in the three months ended in April. The mining equipment maker dropped almost 4%, making it the worst performer on the Dow. Other industrial stocks like United Steel(X) and Alcoa(AA) were also under pressure.

On the heels of Monday's gains, some beat-up momentum stocks continued to make headway despite few major developments. Shares of FireEye(FEYE) climbed 6%, while Pandora Media(P) advanced almost 2%.

Asian markets ended the day on a positive note, though gains were small. Thailand's stock market retreated 1.2% and the country's currency dropped after the Thai army surprised the country by declaring martial law.